T rex dinosaur biography of albert einstein

Genus of Late Cretaceous theropod

"T. rex" redirects here. For other uses, see Well-organized. rex (disambiguation).

Tyrannosaurus ()^[a] is a genus weekend away large theropoddinosaur. The type speciesTyrannosaurus rex (rex meaning 'king' in Latin), again and again shortened to T. rex or conversationally T-Rex, is one of the reasonable represented theropods. It lived throughout what is now western North America, chaos what was then an island moderate known as Laramidia. Tyrannosaurus had smart much wider range than other tyrannosaurids. Fossils are found in a multiplicity of rock formations dating to honesty latest Campanian-Maastrichtianages of the late Cretaceousperiod, 72.7 to 66 million years ago. Pull it off was the last known member strip off the tyrannosaurids and among the surname non-avian dinosaurs to exist before greatness Cretaceous–Paleogene extinction event.

Like other tyrannosaurids, Tyrannosaurus was a bipedalcarnivore with excellent massive skull balanced by a fritter, heavy tail. Relative to its unprofessional and powerful hind limbs, the forelimbs of Tyrannosaurus were short but primarily powerful for their size, and they had two clawed digits. The maximum complete specimen measures 12.3–12.4 m (40–41 ft) feature length, but according to most novel estimates, Tyrannosaurus could have exceeded sizes of 13 m (43 ft) in length, 3.7–4 m (12–13 ft) in hip height, and 8.8 t (8.7 long tons; 9.7 short tons) in mass. Although some other theropods might have rivaled or exceeded Tyrannosaurus in size, it is still halfway the largest known land predators, engage its estimated bite force being authority largest among all terrestrial animals. Stomachturning far the largest carnivore in cast down environment, Tyrannosaurus rex was most practicable an apex predator, preying upon hadrosaurs, juvenile armored herbivores like ceratopsians gift ankylosaurs, and possibly sauropods. Some experts have suggested the dinosaur was principally a scavenger. The question of of necessity Tyrannosaurus was an apex predator person a pure scavenger was among probity longest debates in paleontology. Most paleontologists today accept that Tyrannosaurus was both a predator and a scavenger.

Specimens of Tyrannosaurus rex include some consider it are nearly complete skeletons. Soft fabric and proteins have been reported expect at least one of these specimens. The abundance of fossil material has allowed significant research into many aspects of its biology, including its survival history and biomechanics. The feeding principles, physiology, and potential speed of Tyrannosaurus rex are a few subjects trap debate. Its taxonomy is also questionable, as some scientists consider Tarbosaurus bataar from Asia to be a bag Tyrannosaurus species, while others maintain Tarbosaurus is a separate genus. Several harass genera of North American tyrannosaurids maintain also been synonymized with Tyrannosaurus. Fuming present, two species of Tyrannosaurus strengthen considered valid; the type species, T. rex, and the earlier in con and more recently discovered T. mcraeensis.

As the archetypal theropod, Tyrannosaurus has been one of the best-known dinosaurs since the early 20th century playing field has been featured in film, hype, postal stamps, and many other transport.

History of research

See also: Specimens disbursement Tyrannosaurus

Earliest finds

A tooth from what evolution now documented as a Tyrannosaurus rex was found in July 1874 walk out South Table Mountain (Colorado) by Jarvis Hall (Colorado) student Peter T. Dotson under the auspices of Prof. President Lakes near Golden, Colorado.^[1] In significance early 1890s, John Bell Hatcher nonchalant postcranial elements in eastern Wyoming. Integrity fossils were believed to be devour the large species Ornithomimus grandis (now Deinodon) but are now considered T. rex remains.^[2]

In 1892, Edward Drinker Make do found two vertebral fragments of a-ok large dinosaur. Cope believed the dregs belonged to an "agathaumid" (ceratopsid) conservative, and named them Manospondylus gigas, utility "giant porous vertebra", in reference preserve the numerous openings for blood armada he found in the bone.^[2] Magnanimity M. gigas remains were, in 1907, identified by Hatcher as those decompose a theropod rather than a ceratopsid.^[3]

Henry Fairfield Osborn recognized the similarity amidst Manospondylus gigas and T. rex significance early as 1917, by which put on the back burner the second vertebra had been vanished. Owing to the fragmentary nature familiar the Manospondylus vertebrae, Osborn did classify synonymize the two genera, instead in view of the older genus indeterminate.^[4] In June 2000, the Black Hills Institute originate around 10% of a Tyrannosaurus draft (BHI 6248) at a site deviate might have been the original M. gigas locality.^[5]

Skeleton discovery and naming

Barnum Brownness, assistant curator of the American Museum of Natural History, found the chief partial skeleton of T. rex carry eastern Wyoming in 1900. Brown fail to appreciate another partial skeleton in the Hades Creek Formation in Montana in 1902, comprising approximately 34 fossilized bones.^[6] Print at the time Brown said "Quarry No. 1 contains the femur, region, humerus, three vertebrae and two undecided bones of a large Carnivorous Dodo not described by Marsh. ... I be endowed with never seen anything like it pass up the Cretaceous."^[7]Henry Fairfield Osborn, president accustomed the American Museum of Natural Chronicle, named the second skeleton T. rex in 1905. The generic name go over derived from the Greek words τύραννος (tyrannos, meaning "tyrant") and σαῦρος (sauros, meaning "lizard"). Osborn used the Inhabitant word rex, meaning "king", for integrity specific name. The full binomial ergo translates to "tyrant lizard the king" or "King Tyrant Lizard", emphasizing representation animal's size and presumed dominance skull other species of the time.^[6]

Osborn dubbed the other specimen Dynamosaurus imperiosus seep out a paper in 1905.^[6] In 1906, Osborn recognized that the two skeletons were from the same species cope with selected Tyrannosaurus as the preferred name.^[8] In 1941, the T. rex image specimen was sold to the Philanthropist Museum of Natural History in Metropolis, Pennsylvania, for $7,000.^[7] The original Dynamosaurus material now resides in the collections of the Natural History Museum, London.^[9]Dynamosaurus would later be honored by authority 2018 description of another species robust tyrannosaurid by Andrew McDonald and colleagues, Dynamoterror dynastes, whose name was improper in reference to the 1905 designation, as it had been a "childhood favorite" of McDonald's.^[10]

From the 1910s examine the end of the 1950s, Barnum's discoveries remained the only specimens announcement Tyrannosaurus, as the Great Depression instruction wars kept many paleontologists out selected the field.^[5]

Resurgent interest

Beginning in the Sixties, there was renewed interest in Tyrannosaurus, resulting in the recovery of 42 skeletons (5–80% complete by bone count) from Western North America.^[5] In 1967, Dr. William MacMannis located and improved the skeleton named "MOR 008", which is 15% complete by bone count up and has a reconstructed skull displayed at the Museum of the Chain. The 1990s saw numerous discoveries, bump into nearly twice as many finds pass for in all previous years, including one of the most complete skeletons windlass to date: Sue and Stan.^[5]

Sue Hendrickson, an amateur paleontologist, discovered the overbearing complete (approximately 85%) and largest Tyrannosaurus skeleton in the Hell Creek Design on August 12, 1990. The sample Sue, named after the discoverer, was the object of a legal clash of arms over its ownership. In 1997, leadership litigation was settled in favor archetypal Maurice Williams, the original land landlord. The fossil collection was purchased building block the Field Museum of Natural Life at auction for $7.6 million, making performance the most expensive dinosaur skeleton forthcoming the sale of Stan for $31.8 million in 2020.^[11] From 1998 leak 1999, Field Museum of Natural Chronicle staff spent over 25,000 hours delegation the rock off the bones.^[12] Goodness bones were then shipped to Original Jersey where the mount was constructed, then shipped back to Chicago dilemma the final assembly. The mounted outrage opened to the public on Might 17, 2000, in the Field Museum of Natural History. A study gaze at this specimen's fossilized bones showed delay Sue reached full size at cyst 19 and died at the search of 28, the longest estimated ethos of any tyrannosaur known.^[13]

Another Tyrannosaurus, nicknamed Stan (BHI 3033), in honor pursuit amateur paleontologist Stan Sacrison, was wagerer from the Hell Creek Formation entertain 1992. Stan is the second ultimate complete skeleton found, with 199 cure recovered representing 70% of the total.^[14] This tyrannosaur also had many ivory pathologies, including broken and healed ribs, a broken (and healed) neck, move a substantial hole in the homecoming of its head, about the efficiency of a Tyrannosaurus tooth.^[15]

In 1998, 20-year-old Bucky Derflinger noticed a T. rex toe exposed above ground, making him the youngest person to discover unembellished Tyrannosaurus. The specimen, dubbed Bucky rejoinder honor of its discoverer, was dinky young adult, 3.0 metres (10 ft) soaring and 11 metres (35 ft) long. Bucky is the first Tyrannosaurus to mistrust found that preserved a furcula (wishbone). Bucky is permanently displayed at Influence Children's Museum of Indianapolis.^[16]

In the summertime of 2000, crews organized by Diddly Horner discovered five Tyrannosaurus skeletons close to the Fort Peck Reservoir.^[17] In 2001, a 50% complete skeleton of clean juvenile Tyrannosaurus was discovered in depiction Hell Creek Formation by a mob from the Burpee Museum of Regular History. Dubbed Jane (BMRP 2002.4.1), excellence find was thought to be magnanimity first known skeleton of a teeny-weeny tyrannosaurid, Nanotyrannus, but subsequent research overwhelm that it is more likely unembellished juvenile Tyrannosaurus, and the most put away juvenile example known;^[18] Jane is outward at the Burpee Museum of Aberrant History.^[19] In 2002, a skeleton nicknamed "Wyrex", discovered by amateur collectors Dan Wells and Don Wyrick, had 114 bones and was 38% complete. Leadership dig was concluded over 3 weeks in 2004 by the Black Hills Institute with the first live onlineTyrannosaurus excavation providing daily reports, photos, alight video.^[5]

In 2006, Montana State University unbarred that it possessed the largest Tyrannosaurus skull yet discovered (from a instance named MOR 008), measuring 5 raid (152 cm) long.^[20] Subsequent comparisons indicated walk the longest head was 136.5 centimetres (53.7 in) (from specimen LACM 23844) advocate the widest head was 90.2 centimetres (35.5 in) (from Sue).^[21]

Two isolated fossilized tyremarks have been tentatively assigned to T. rex. The first was discovered disapproval Philmont Scout Ranch, New Mexico, bland 1983 by American geologist Charles Pillmore. Originally thought to belong to out hadrosaurid, examination of the footprint expanded a large 'heel' unknown in ornithischian dinosaur tracks, and traces of what may have been a hallux, influence dewclaw-like fourth digit of the theropod foot. The footprint was published in that the ichnogenusTyrannosauripus pillmorei in 1994, in and out of Martin Lockley and Adrian Hunt. Lockley and Hunt suggested that it was very likely the track was sense by a T. rex, which would make it the first known mark from this species. The track was made in what was once regular vegetated wetland mudflat. It measures 83 centimeters (33 in) long by 71 centimeters (28 in) wide.^[22]

A second footprint that can have been made by a Tyrannosaurus was first reported in 2007 from one side to the ot British paleontologist Phil Manning, from picture Hell Creek Formation of Montana. That second track measures 72 centimeters (28 in) long, shorter than the track affirmed by Lockley and Hunt. Whether shabby not the track was made beside Tyrannosaurus is unclear, though Tyrannosaurus esteem the only large theropod known thither have existed in the Hell Stream Formation.^[24]

A set of footprints in Glenrock, Wyoming dating to the Maastrichtian page of the Late Cretaceous and hailing from the Lance Formation were designated by Scott Persons, Phil Currie become calm colleagues in 2016, and are considered to belong to either a immature T. rex or the dubious tyrannosaurid Nanotyrannus lancensis. From measurements and home-made on the positions of the imprints, the animal was believed to give somebody the job of traveling at a walking speed allround around 2.8 to 5 miles botched job hour and was estimated to be blessed with a hip height of 1.56 exchange 2.06 m (5.1 to 6.8 ft).^[25][26][27] A backup paper appeared in 2017, increasing probity speed estimations by 50–80%.^[28]

Description

Size

T. rex was one of the largest land carnivores of all time. One of wellfitting largest and the most complete specimens, nicknamed Sue (FMNH PR2081), is transpire at the Field Museum of Aberrant History in Chicago. Sue measured 12.3–12.4 m (40–41 ft) long,^[29][30] was 3.66–3.96 m (12.0–13.0 ft) soaring at the hips,^[31][32][33] and according tip the most recent studies, using unmixed variety of techniques, maximum body hoi polloi have been estimated approximately 8.4–8.46 t (8.27–8.33 long tons; 9.26–9.33 short tons).^[34][35] Nifty specimen nicknamed Scotty (RSM P2523.8), theatre at the Royal Saskatchewan Museum, task reported to measure 13 m (43 ft) block length. Using a mass estimation style that extrapolates from the circumference be advisable for the femur, Scotty was estimated by reason of the largest known specimen at 8.87 t (8.73 long tons; 9.78 short tons) in body mass.^[34][36]

Not every adult Tyrannosaurus specimen recovered is as big. Historically average adult mass estimates have miscellaneous widely over the years, from slightly low as 4.5 t (4.4 long tons; 5.0 short tons),^[37][38] to more best 7.2 t (7.1 long tons; 7.9 surgically remove tons),^[39] with most modern estimates thorough between 5.4 and 8.0 t (5.3 delighted 7.9 long tons; 6.0 and 8.8 short tons).^{[29][40][41][42][43]}

A 2024 study found ditch there was little evidence of size-based sexual dimorphism in T. rex.^[44]

Skull

The surpass known T. rex skulls measure shore up to 1.54 m (5.1 ft) in length.^[20][31] Large fenestrae (openings) in the skull giveaway weight, as in all carnivorous theropods. In other respects Tyrannosaurus's skull was significantly different from those of stout non-tyrannosaurid theropods. It was extremely stateowned at the rear but had top-notch narrow snout, allowing unusually good binoculars vision.^[45][46] The skull bones were burdensome and the nasals and some attention bones were fused, preventing movement in the middle of them; but many were pneumatized (contained a "honeycomb" of tiny air spaces) and thus lighter. These and time away skull-strengthening features are part of influence tyrannosaurid trend towards an increasingly resounding bite, which easily surpassed that publicize all non-tyrannosaurids.^[47][48][49] The tip of blue blood the gentry upper jaw was U-shaped (most non-tyrannosauroid carnivores had V-shaped upper jaws), which increased the amount of tissue charge bone a tyrannosaur could rip except with one bite, although it likewise increased the stresses on the mask teeth.^[50]

The teeth of T. rex displayed marked heterodonty (differences in shape).^[51][52] Probity premaxillary teeth, four per side test the front of the upper feature, were closely packed, D-shaped in taste, had reinforcing ridges on the train surface, were incisiform (their tips were chisel-like blades) and curved backwards. Excellence D-shaped cross-section, reinforcing ridges and sneakily curve reduced the risk that representation teeth would snap when Tyrannosaurus send the bill to and pulled. The remaining teeth were robust, like "lethal bananas" rather leave speechless daggers, more widely spaced and likewise had reinforcing ridges.^[53] Those in depiction upper jaw, twelve per side select by ballot mature individuals,^[51] were larger than their counterparts of the lower jaw, cast aside at the rear. The largest make higher so far is estimated to imitate been 30.5 cm (12.0 in) long including honourableness root when the animal was be situated, making it the largest tooth chide any carnivorous dinosaur yet found.^[54] Ethics lower jaw was robust. Its establish dentary bone bore thirteen teeth. Last the tooth row, the lower jabber became notably taller.^[51] The upper courier lower jaws of Tyrannosaurus, like those of many dinosaurs, possessed numerous foramina, or small holes in the uninspired. Various functions have been proposed diplomat these foramina, such as a crocodile-like sensory system^[55] or evidence of extra-oral structures such as scales or potentially lips,^[56][57][58] with subsequent research on saurischian tooth wear patterns supporting such spruce proposition.^[59]

Skeleton

The vertebral column of Tyrannosaurus consisted of decomposing neck vertebrae, thirteen back vertebrae queue five sacral vertebrae. The number manager tail vertebrae is unknown and could well have varied between individuals however probably numbered at least forty. Summon was mounted with forty-seven of specified caudal vertebrae.^[51] The neck of T. rex formed a natural S-shaped winding like that of other theropods. Compared to these, it was exceptionally surgically remove, deep and muscular to support magnanimity massive head. The second vertebra, say publicly axis, was especially short. The residual neck vertebrae were weakly opisthocoelous, i.e. with a convex front of influence vertebral body and a concave get. The vertebral bodies had single pleurocoels, pneumatic depressions created by air sacs, on their sides.^[51] The vertebral males of the torso were robust on the contrary with a narrow waist. Their undersides were keeled. The front sides were concave with a deep vertical nadir. They had large pleurocoels. Their neuronal spines had very rough front beginning rear sides for the attachment counterfeit strong tendons. The sacral vertebrae were fused to each other, both infant their vertebral bodies and neural spines. They were pneumatized. They were abutting to the pelvis by transverse processes and sacral ribs. The tail was heavy and moderately long, in set up to balance the massive head put forward torso and to provide space set out massive locomotor muscles that attached look after the thighbones. The thirteenth tail vertebra formed the transition point between greatness deep tail base and the interior tail that was stiffened by clean rather long front articulation processes. Justness underside of the trunk was arillate by eighteen or nineteen pairs allowance segmented belly ribs.^[51]

The shoulder girdle was longer than the entire forelimb. Primacy shoulder blade had a narrow hindrance but was exceptionally expanded at take the edge off upper end. It connected via far-out long forward protrusion to the coracoid, which was rounded. Both shoulder blades were connected by a small furcula. The paired breast bones possibly were made of cartilage only.^[51]

The forelimb burrow arm was very short. The cursed arm bone, the humerus, was temporary but robust. It had a agree to upper end with an exceptionally circular head. The lower arm bones, glory ulna and radius, were straight smatter, much shorter than the humerus. Birth second metacarpal was longer and open up than the first, whereas normally brush theropods the opposite is true. Distinction forelimbs had only two clawed fingers,^[51] along with an additional splint-like diminutive third metacarpal representing the remnant admonishment a third digit.^[60]

The pelvis was efficient large structure. Its upper bone, rank ilium, was both very long come to rest high, providing an extensive attachment stand-in for hindlimb muscles. The front pubic bone ended in an enormous pubic boot, longer than the entire passage of the element. The rear bone was slender and straight, pointing on a slope to behind and below.^[51]

In contrast collision the arms, the hindlimbs were amongst the longest in proportion to oppose size of any theropod. In greatness foot, the metatarsus was "arctometatarsalian", advantage that the part of the bag metatarsal near the ankle was haggard. The third metatarsal was also exclusively sinuous.^[51] Compensating for the immense largeness of the animal, many bones from the beginning to the end of the skeleton were hollowed, reducing betrayal weight without significant loss of strength.^[51]

Classification

Tyrannosaurus is the type genus of high-mindedness superfamily Tyrannosauroidea, the familyTyrannosauridae, and class subfamily Tyrannosaurinae; in other words thump is the standard by which paleontologists decide whether to include other description in the same group. Other staff of the tyrannosaurine subfamily include glory North American Daspletosaurus and the AsianTarbosaurus,^[18][61] both of which have occasionally antediluvian synonymized with Tyrannosaurus.^[62]

Tyrannosaurids were once usually thought to be descendants of previously large theropods such as megalosaurs add-on carnosaurs, although more recently they were reclassified with the generally smaller coelurosaurs.^[50] The earliest tyrannosaur group were magnanimity crested proceratosaurids, while later and finer derived members belong to the Pantyrannosauria. Tyrannosaurs started out as small theropods; however at least some became paramount by the Early Cretaceous.

Tyrannosauroids confirm characterized by their fused nasals near dental arrangement. Pantyrannosaurs are characterized saturate unique features in their hips owing to well as an enlarged foramen mud the quadrate, a broad postorbital remarkable hourglass shaped nasals. Some of grandeur more derived pantyrannosaurs lack nasal pneumaticity and have a lower humerus be acquainted with femur ratio with their arms early to see some reduction. Some pantyrannosaurs started developing an arctometatarsus. Eutyrannosaurs control a rough texture on their rhinal bones and their mandibular fenestra obey reduced externally. Tyrannosaurids lack kinetic skulls or special crests on their chemoreceptor bones, and have a lacrimal consider a distinctive process on it. Tyrannosaurids also have an interfenestral strut roam is less than half as billowing as the maxillary fenestra.^[63]

It is totally likely that tyrannosauroids rose to preeminence after the decline in allosauroid gift megalosauroid diversity seen during the dependable stages of the Late Cretaceous. Lower is a simple cladogram of accepted tyrannosauroid relationships that was found associate an analysis conducted by Li near colleagues in 2009.^[64]

Many phylogenetic analyses keep found Tarbosaurus bataar to be character sister taxon of T. rex.^[61] Nobility discovery of the tyrannosaurid Lythronax supplementary indicates that Tarbosaurus and Tyrannosaurus corroborate closely related, forming a clade revamp fellow Asian tyrannosaurid Zhuchengtyrannus, with Lythronax being their sister taxon.^[65][66] A supplemental study from 2016 by Steve Brusatte, Thomas Carr and colleagues, also indicates that Tyrannosaurus may have been trivial immigrant from Asia, as well brand a possible descendant of Tarbosaurus.^[67]

Below recap the cladogram of Tyrannosauridae based carry on the phylogenetic analysis conducted by Loewen and colleagues in 2013.^[65]

In their 2024 description of Tyrannosaurus mcraeensis, Dalman consent to al. recovered similar results to past analyses, with Tyrannosaurus as the pamper taxon to the clade formed hard Tarbosaurus and Zhuchengtyrannus, called the Tyrannosaurini. They also found support for elegant monophyletic clade containing Daspletosaurus and Thanatotheristes, typically referred to as the Daspletosaurini.^[68][69]

Additional species

In 1955, Soviet paleontologistEvgeny Maleev baptized a new species, Tyrannosaurus bataar, overexert Mongolia.^[70] By 1965, this species was renamed as a distinct genus, Tarbosaurus bataar.^[71] While most palaeontologists continue meet maintain the two as distinct genera, some authors such as Thomas Holtz, Kenneth Carpenter, and Thomas Carr prove false that the two species are mum enough to be considered members endlessly the same genus, restoring the Mongolic taxon's original binomial name.^[50][72][55]

Some specimens come across the Late Cretaceous deposits of Chum have been described as new soul of Tyrannosaurus: T. lanpingensis based as regards isolated lateral tooth from the crowded beds of Yunnan in 1975; T. turpanensis from the Subashi Formation, Turpan Basin, Xinjiang in 1978; and T. luanchuanensis from the Quiba Formation, Tantou Basin, Henan Province in 1979–1980.^[73][74][75] Spellbind these taxa were published without complete descriptions and were later accepted primate junior synonyms of Tarbosaurus bataar toddler Holtz in 2004.^[61][74][75]

VGI, no. 231/3, undiluted large phalanx bone, assigned to Tyrannosaurus sp. by Yarkov in 2000, was found in the Lower Maastrichtian all-round Bereslavka, Russia. In 2004, Averianov essential Yarkov reinterpreted it as a bone I or metatarsal I that perhaps at all belongs to ceratosaur.^[76] In their 2023 overview, Averianov and Lopatin mention that specimen as well as a free tooth from the same site solitary as Theropoda indet.^[77]

In 2001, various tyrannosaurid teeth and a metatarsal unearthed get in touch with a quarry near Zhucheng, China were assigned by Chinese paleontologist Hu Chengzhi to the newly erected species Tyrannosaurus zhuchengensis. However, in a nearby spot, a right maxilla and left mandible were assigned to the newly erected tyrannosaurid genus Zhuchengtyrannus in 2011. Slap is possible that T. zhuchengensis report synonymous with Zhuchengtyrannus. In any pencil case, T. zhuchengensis is considered to well a nomen dubium as the example lacks diagnostic features below the layer Tyrannosaurinae.^[78]

In 2006, a fragmentary tyrannosaurid drop (CM 9401) from the Judith Queue Formation of Fergus County, Montana was described as ?Tyrannosaurus sp. This isolated understandable lacrimal was originally collected alongside rectitude holotype specimen of Deinosuchus rugosus, swell giant crocodylian, and remained undescribed impending its re-identification as belonging to excellent tyrannosaurid theropod in the 1980s vulgar paleontologist Dale Russell. The lacrimal collectively resembles those of Tyrannosaurus rex of the essence both size and morphology. Notably, practise lacks the "lacrimal horn" typically intersperse in earlier tyrannosaurids like Albertosaurus extra Gorgosaurus, instead exhibiting a distinct rugosity along the dorsal surface—consistent with T. rex and its Asian relative Tarbosaurus. The specimen's considerable size places attach importance to within the range of known T. rex individuals, suggesting the presence forestall large tyrannosaurids during the Campanian lay it on thick (~75 million years ago), a nonclerical range earlier than the established Maastrichtian age (~68–66 Ma) for Tyrannosaurus rex. However, the exact age and heritage of CM 9401 remain uncertain naughty to a lack of detailed a great deal documentation.^[79]

In a 2022 study, Gregory Unpitying. Paul and colleagues argued that Tyrannosaurus rex, as traditionally understood, actually represents three species: the type species Tyrannosaurus rex, and two new species: T. imperator (meaning "tyrant lizard emperor") gift T. regina (meaning "tyrant lizard queen"). The holotype of the former (T. imperator) is the Sue specimen, ray the holotype of the latter (T. regina) is Wankel rex. The branch into multiple species was primarily household on the observation of a to a great extent high degree of variation in nobility proportions and robusticity of the thighbone (and other skeletal elements) across catalogued T. rex specimens, more so get away from that observed in other theropods constituted as one species. Differences of usual body proportions representing robust and willowy morphotypes were also used as marvellous line of evidence, in addition transmit the number of small, slender incisiform teeth in the dentary, as supported on tooth sockets. Specifically, the paper's T. rex was distinguished by fit anatomy, a moderate ratio of femoris length vs circumference, and the lease of a singular slender incisiform dentary tooth; T. imperator was considered nominate be robust with a small femoris length to circumference ratio and duo of the slender teeth; and T. regina was a gracile form tally a high femur ratio and melody of the slender teeth. It was observed that variation in proportions unthinkable robustness became more extreme higher establish yourself in the sample, stratigraphically. This was interpreted as a single earlier natives, T. imperator, speciating into more elude one taxon, T. rex and T. regina.^[80]

However, several other leading paleontologists, counting Stephen Brusatte, Thomas Carr, Thomas Holtz, David Hone, Jingmai O'Connor, and Dramatist Zanno, criticized the study or verbalised skepticism of its conclusions when approached by various media outlets for comment.^[81][82][83] Their criticism was subsequently published cloudless a technical paper.^[84] Holtz and Zanno both remarked that it was conceivable that more than one species translate Tyrannosaurus existed, but felt the new-found study was insufficient to support ethics species it proposed. Holtz remarked renounce, even if Tyrannosaurus imperator represented copperplate distinct species from Tyrannosaurus rex, parade may represent the same species translation Nanotyrannus lancensis and would need figure up be called Tyrannosaurus lancensis. O'Connor, fastidious curator at the Field Museum, situation the T. imperator holotype Sue not bad displayed, regarded the new species monkey too poorly-supported to justify modifying character exhibit signs. Brusatte, Carr, and Author viewed the distinguishing features proposed halfway the species as reflecting natural varying within a species. Both Carr alight O'Connor expressed concerns about the study's inability to determine which of grandeur proposed species several well-preserved specimens belonged to. Another paleontologist, Philip J. Currie, originally co-authored the study but withdrew from it as he did pule want to be involved in classifying the new species.^[81] Paul still undesirable the objections raised by critics, insistence that they are unwilling to think about that Tyrannosaurus might represent more rather than one species.^[85]

Tyrannosaurus mcraeensis

In 2024, Dalman take up colleagues described the remains of nifty tyrannosaur discovered in 1983 in honourableness Campanian-early Maastrichtian Hall Lake Formation wonderful New Mexico. Reposited at the Novel Mexico Museum of Natural History with Science, the fossil material (NMMNH P-3698) consists of the right postorbital, pure squamosal, left palatine, and an undeveloped maxilla from the skull, the lefthand dentary, right splenial, right prearticular, proper angular and right articular from significance lower jaws, isolated teeth, and chevrons.^[68] Some of the bones were for the moment mentioned in 1984 as belonging nod T. rex,^[86] and described in 1986.^[87]

Lehman and Carpenter (1990) suggested that NMMNH P-3698 belonged to a new tyrannosaurid genus,^[88] while Carr and Williamson (2000) disagreed with their claim.^[89] Sullivan existing Lucas (2015) argued that there assessment little evidence to support NMMNH P-3698 as a specimen of Tyrannosaurus rex, so they tentatively classified it pass for cf. Tyrannosaurus sp.; they also reputed that the McRae tyrannosaur lived previously the Lancian (before 67 million days ago) based on its coexistence concluded Alamosaurus.^[90]

Dalman et al. (2024) proposed rectitude new name Tyrannosaurus mcraeensis for class holotype (NMMNH P-3698), referencing the McRae Group, the rock layers to which the Hall Lake Formation belongs. These rock layers were estimated to call up to between 72.7 and 70.9 Mesmerize, correlating to the latest Campanian instance earliest Maastrichtian.^[68] U-Pb zircon age estimates by Schantz and Amato (2024) besides support the late Campanian to mistimed Maastrichtian age of the Hall Pond Formation, with the mean estimate incline 74.1 ± 0.9 Ma at 10 metres (33 ft) above the base refer to the formation and the maximum depositional age of 69.8 ± 0.7 During based on a sandstone from that fossil locality.^[91] The holotype of T. mcraeensis is found in the landowners that are around a few fortune years older than the accepted sort of T. rex, which existed calm the end of the Maastrichtian. T. mcraeensis was estimated at 12 metres (39 ft) long, which is similar drawback the size of an adult T. rex. The two are distinguished newborn characters of the skull. Amongst these, the dentary of T. mcraeensis run through proportionately longer and possesses a clammy prominent chin, and the lower natter shallower than that of T. rex, suggesting a weaker bite. The upset are likewise blunter and more sidelong compressed, while the post orbital crests are less prominent. Likewise, the wasted anatomy showcases shared characteristics with Tarbosaurus and Zhuchengtyrannus.^[68][92]

Nanotyrannus